X-Men: Dark Phoenix was expected to close the main X-franchise that started back in 2000, but it ended up being so underwhelming and the box office numbers are not looking good. As it turns out, the movie was planned to be a two-parter, and we would have seen the return of an X-Men: Apocalypse cast member.
As per MCU Cosmic, Olivia Munn's Psylocke was supposed to return for the film, and she would have been the other telepath working with Magneto. Munn had told Collider earlier, "It's like a two parter, this movie. That's more than I've said, in general. I don't know why people have to be so secretive."
What's more, the movie's original ending would have definitely been similar to Captain Marvel, what with the Shi'ar ships appearing in the end then being taken out by Jean in her fill Phoenix form. Also, the main alien enemies that could shapeshift into humans? They were supposed to be Skrulls.
Had the movie stuck to its original release date for November of last year, I'm sure it would have been Captain Marvel getting the criticisms for copying Dark Phoenix, but test audiences already weren't pleased with what was originally put together.
If you ask me, the franchise kind of went downhill after First Class. Sure we have gems like Logan and Deadpool, but the timeline got all messed up since Days of Future Past. How is it that everyone from FC hasn't aged in 30 years? If you ask me, they should have just stuck to the earlier timeline and didn't rush to connect the dots with the first generation of X-Men.
For now, you can catch Dark Phoenix in theaters.